The invention relates to an internal combustion engine having at least one piston which performs stroke movements in a cylinder crankcase and which, via two connecting rods, interacts with two parallel crankshafts which rotate synchronously in opposite directions.
A reciprocating-piston assembly is known, from EP 2 426 336 A2, which includes a reciprocating piston. The reciprocating piston is connected via two connecting rods to two crankshafts which are oriented parallel to one another. Each crankshaft is equipped with a synchronization gearwheel, wherein the two synchronization gearwheels are in the form of spur gears and are in engagement with one another such that said gearwheels rotate synchronously with the crankshafts in opposite directions.
In the case of assemblies of this type of construction, adverse addition of manufacturing tolerances, thermal influences during operation or wear on the tooth flanks of the synchronization gearwheels may give rise to a clearance between the intermeshing synchronization gearwheels. This clearance gives rise to an asymmetry during the rotation of the two crankshafts, which asymmetry can lead to undesired tilting of the piston in the cylinder of the reciprocating-piston assembly. Owing to the asymmetry of the rotation of the crankshafts, the crankshafts duly rotate in temporally synchronized fashion in opposite directions but, during the rotation of the two crankshafts, one of the crankshafts leads the other crankshaft, such that the crankshaft-side connecting rod spindles reach their top dead center not simultaneously but successively. This has the result that the piston-side connecting rod bearings also reach their top dead center temporally in succession, which results in a tilting movement of the piston. The advance of one crankshaft in relation to the other crankshaft exists throughout the rotation of the synchronized crankshafts, giving rise to the stated systemic asymmetry. The latter has the effect that, when the piston is at top dead center, a tilting moment toward one side acts on the piston, and when the piston is at bottom dead center, a corresponding tilting moment toward the other side acts on the piston.
To compensate the asymmetry of the rotation of the two crankshafts, it is provided in the above-cited EP 2 426 336 A2 that the piston-side pivot bearings of the connecting rod are articulatedly connected to a device which, in the form of a cylindrical bearing element, is pivotably articulated in a bearing bore of the piston. A tilting of the piston, with its piston longitudinal axis, relative to the cylinder longitudinal axis is thereby counteracted.
DE 10 2006 036 827 B4 discloses a power or working machine with a single reciprocating piston and with two crankshafts which extend parallel to one another with a spacing. Two connecting rods act between the oppositely rotating crankshafts, which are in engagement by way of synchronization gearwheels, and the reciprocating piston. In order that tilting of the piston in the cylinder caused by the asymmetry during the rotation of the two crankshafts does not have an adverse effect on the functional back-and-forth movement of the reciprocating piston, the reciprocating piston is designed as follows: in a cross-sectional plane lying perpendicular to the axes of rotation of the crankshafts, the reciprocating piston has a radius which varies along the piston axis. This is such that the piston has, adjacent to the cylinder inner wall, a region which has a greater diameter than the piston regions above and below the region. Even in the event of slight tilting of the piston, only the relatively short section of the piston with the largest diameter makes contact with the piston wall. In this way, the risk of jamming of the piston is greatly reduced.
It is an object of the invention to design a high-grade reciprocating-piston assembly with a reciprocating piston and with two crankshafts which are arranged parallel to one another and which are connected by way of connecting rods to the reciprocating piston, and a device for compensating an asymmetry of the rotation of the crankshafts. Here, it should be ensured that the device can be easily realized and contributes to good functioning of the reciprocating-piston assembly.
This and other objects are achieved in accordance with the invention by an internal combustion engine having at least one piston which performs stroke movements in a cylinder crankcase and which, via two connecting rods, interacts with two parallel crankshafts which rotate synchronously in opposite directions, wherein the connecting rods have, on a side facing toward a piston crown of the piston, bearing eyelets which, via piston pins, are operatively connected to the first and second bearings provided at opposite first and second sides of the piston. These bearings and piston pins act as a device for compensating an asymmetry of the profile of the crankshafts, wherein the first and the second bearings for the device have cylindrical bearing disks which, firstly, are rotatably mounted in piston bores and which, secondly, comprise disk bores for receiving first and second pin sections of the piston pins.
The main advantages attained with the invention can be seen in the fact that the device for compensating a possible asymmetry of the profile of the crankshafts contributes to the efficient operation of the internal combustion engine in an ideal manner. This is assisted by the two standard-setting cylindrical bearing disks and the piston pins which, with regard to structural design, can be produced easily and under expedient conditions. The bearing disks are received by the piston bores in an excellent manner; likewise, the first and second pin sections of the piston pins in the disk bores. It is to be emphasized that, owing to the different diameters of the pin sections it is possible for there to be provided on the respective piston pin a step with a collar in the form of a stop, which collar is supported on an inner side of an associated bearing disk. The laterally reversed arrangement of the piston pins ensures a targeted transmission of force from the piston to the connecting rods. Commercially available, inexpensive circlips, which act between the piston bores and the bearing disks, are suitable for axially securing the bearing disks; corresponding circlips may also be used between the piston pins and the bearing disks. Owing to the sophisticated structural solution of the piston pins, that is to say the step with a collar in the form of a stop, in each case only one circlip is required to axially secure the piston pins in the pin bores. Finally, the bearing disks are equipped with thickened disk portions in the region of the first and second pin sections in order to realize an advantageous bearing base.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.